/Engine/Source/Editor/UnrealEd/Public/WorkflowOrientedApp/WorkflowCentricApplication.h
Registers toolbar for a mode if not already registered
nullptr if toolbar already registered.
virtual [UToolMenu](API\Developer\ToolMenus\UToolMenu) * RegisterModeToolbarIfUnregistered ( const [FName](API\Runtime\Core\UObject\FName) InModeName )